Flat panel displays have recently been developed for visually displaying information generated by computers and other electronic devices. These displays can be made lighter and require less power than conventional cathode ray tube displays. One type of flat panel display is known as a cold cathode field emission display (FED).
A field emission display uses electron emissions to illuminate a cathodoluminescent display screen (termed herein a "faceplate") and generate a visual image. An individual field emission pixel typically includes emitter sites formed on a baseplate. The baseplate includes the circuitry and devices that control electron emission from the emitter sites. A gate electrode structure, or grid, is associated with the emitter sites. The emitter sites and grid are electrically connected to a voltage source. The voltage source establishes a voltage differential between the emitter sites and grid and controls electron emission from the emitter sites. The emitted electrons pass through a vacuum space and strike phosphors contained on the display screen. The phosphors are excited to a higher energy level and release photons to form an image. In this system the display screen is the anode and the emitter sites are the cathode.
The emitter sites and faceplate are spaced apart by a small distance to stand off the voltage difference between them and to provide a gap for gas flow. In order to provide a uniform resolution, focus and brightness at the faceplate, it is important that this distance be uniform across the total surface of the faceplate. In addition, in order to achieve reliable display operation during electron emission from the emitter sites, a vacuum on the order of 10.sup.-6 Torr or less is required. The vacuum is formed in a sealed space contained within the field emission display.
In the past, field emission displays have been constructed as a package having a seal for sealing the space between the baseplate and faceplate. Typically, some type of a tube must also be provided for evacuating this space during construction of the field emission display package. The tube provides a conduit for pumping gases out of the sealed space to form a vacuum. After forming the vacuum, the tube must also be sealed by pinching or by affixing a sealing member such as a plug.
One problem with this type of tubulated package is that the tube is a permanent part of the assembly. The tube requires a separate sealing operation and a separate seal. Moreover, the tube represents an additional component that can potentially fail during the lifetime of the field emission display package. The protrusion of the tube from the display body is inconvenient and must be accommodated during packaging of the display into a system, such as a lap top computer.
It would be advantageous if a field emission display package could be formed without an evacuation tube. This would simplify the package and eliminate a potential source of failure. It would also be advantageous to be able to seal the field emission display package and activate a getter at the same time that the vacuum is formed. This would simplify the manufacturing process.